1. Field of the Invention
The present invention relates to a method for the formation of a semiconductor layer (or semiconductor layers), and more particularly to a method for the formation of a semiconductor layer (layers) suitable for applying in case of forming an epitaxial semiconductor layer (or layers) of, for example, a GaN (gallium nitride) or the like thin, thick or the like film(s) on a substrate or the like made of a variety of materials.
2. Description of the Related Art
In recent years, attention is being given to GaN being an nitride semiconductor of the groups III-V as a light-emitting device material in a short wavelength region such as blue wavelength region to ultraviolet wavelength region, and in this connection, blue light emitting diode (LED) prepared from a GaN system thin film material has been realized, besides developments for blue laser prepared from such GaN system thin film material are proceeding.
As such GaN system thin films, not only GaN, but also, for example, a light-emitting device material prepared from InGaN and the like are known.
In order to improve efficiency in light emission or to realize blue laser prepared from a GaN system thin film material, it has been considered to be important that structural defects, for example, mis fit dislocations, dislocations such as threading dislocations derived from misfit dislocations, grain boundaries and the like existing in a GaN system thin film are favorably controlled.
Meanwhile, a defect density (the number of structural defects per unit area) of a GaN thin film formed on sapphire (Al2O3)which has been widely used as a substrate indicates an extremely high value.
Such a high value of the defect density in GaN system thin film is principally due to lattice mismatch of a GaN system thin film with a substrate material (Al2O3) as well as a difference in thermal expansion coefficient between them. In this respect, a high value of defect density in a GaN system thin film has been considered to be an unavoidable problem in view of an actual status where no substrate which is appropriately used as a GaN substrate and which is in good lattice match with a GaN system thin film exists.
For the sake of improving a high defect density in a GaN thin film, as shown in FIG. 1 illustrating schematically a thin film structure, such a manner that, for example, a 6Hxe2x80x94SiC (0001) substrate being a type of SiC substrate is used, an AlN thin film is formed thereon (in a thickness of, for example, 10 nm or thicker), and a GaN system thin film is further formed thereon (in a thickness of, for example, 1.5 xcexcm) has been applied heretofore.
Namely, since an AlN thin film has 1% of a rate of lattice mismatch with an SiC substrate, and on one hand, it exhibits a rate of lattice mismatch of 2.5% with a GaN thin film, such AlN thin film has been used as a buffer layer between the SiC substrate and the GaN system thin film.
In the thin film structure shown in FIG. 1 wherein GaN having 1.5 xcexcm thickness is formed on the AlN thin film having a thickness of 10 nm or thicker, although a dislocation density of 109 cmxe2x88x922 order was obtained as to threading dislocation in structural defects, it has been further desired to reduce remarkably dislocation density.
In view of such request, for instance, a manner of ELO (Epitaxial Lateral Overgrowth) process shown in FIGS. 2(a) and 2(b) has been lately proposed.
In the ELO process, first, crystal growth of GaN is made on a substrate 200 through a buffer layer 202 to form a first GaN layer 204 as a result of the crystal growth of GaN, and then, a mask 206 is formed on the first GaN layer 204 with the use of a predetermined mask pattern (see FIG. 2(a)).
Thereafter, further crystal growth of GaN is made on the first GaN layer 204 on which has been formed the mask 206 to form a second GaN layer 208, whereby it is intended to reduce a dislocation density of threading dislocations in the second GaN layer 208 (see FIG. 2(b)).
According to the above described ELO process, threading dislocations appear in the first GaN layer 204 at a dislocation density of 10 to 1010 cmxe2x88x922 order, while GaN crystal grown from the first GaN layer 204 which has not been covered by the mask 206 comes to grow laterally (directions indicated by the arrows in FIG. 2(b)) on the mask 206, so that a dislocation density of threading dislocations in the second GaN layer 208 was reduced to 107 cmxe2x88x922 order.
In the above described ELO process, however, it is required to form the mask 206 on the first GaN layer 204 with the use of a predetermined mask pattern (see FIG. 2(a)). Accordingly, there have been such problems that a variety of processes of operation such as etching are required, whereby working hours extend over a long period of time as well as that its manufacturing cost and the like increase, so that the resulting products become expensive.
Moreover, there has been such a further problem that according to ELO process, threading dislocations appear in the second GaN layer 208 within boundary portions where GaN crystals each grown laterally by the use of the mask 206 fuse with each other (portions indicated by dotted lines in FIG. 2(b)), so that when it is arranged in such that the second GaN layer 208 containing the boundary portions is not used for a device such as blue LED, a region of a GaN system thin film which can be used for a device and the like is restricted.
The present invention has been made in view of various problems involved in the prior art as described above, and an object of the invention is to provide a method for the formation of a semiconductor layer (layers) by which a defect density of structural defects, particularly a dislocation density of threading dislocations in the resulting semiconductor layer(s) can be remarkably reduced, so that hours of work can be shortened as well as a manufacturing cost can be reduced without requiring any complicated process in case of forming a semiconductor layer (layers) of, for example, a GaN (gallium nitride) or the like thin, thick or the like film(s) on a substrate or the like made of a variety of materials.
In order to achieve the above described objects, in the present invention, a method for the formation of a semiconductor layer for forming the semiconductor layer comprises supplying a structural defect suppressing material for suppressing structural defects in the semiconductor layer.
Therefore, according to the present invention, since a structural defect suppressing material for suppressing structural defects in a semiconductor is supplied, such structural defect suppressing material is adsorbed or applied at a position where a structural defect, and particularly threading dislocation appears on a surface of a material layer on which is to be formed the semiconductor layer, so that structural defects, particularly threading dislocations in the semiconductor layer are suppressed, whereby a dislocation density can be significantly reduced.
Furthermore, in the present invention, a method for the formation of a semiconductor layer for forming the semiconductor layer comprises supplying a structural defect suppressing material for suppressing structural defects in the semiconductor layer onto a surface of the layer of a material from which the semiconductor layer is to be formed.
Therefore, according to the invention, since a structural defect suppressing material for suppressing structural defects in a semiconductor is supplied onto a surface of the layer of a material from which the semiconductor layer is to be formed, the structural defect suppressing material is adsorbed or applied at a position where a structural defect, and particularly threading dislocation appears on a surface of the layer of a material on which is to be formed the semiconductor layer, so that structural defects, particularly threading dislocations in the semiconductor layer are suppressed, whereby a dislocation density can be significantly reduced.
Moreover, in the present invention, a method for the formation of a semiconductor layer for forming the semiconductor layer comprises supplying simultaneously a structural defect suppressing material for suppressing structural defects in the semiconductor layer with a material from which the semiconductor layer is to be formed in case of forming the semiconductor layer.
Therefore, according to the invention, since a structural defect suppressing material for suppressing structural defects in a semiconductor is supplied simultaneously with a material from which the semiconductor layer is to be formed, the structural defect suppressing material is adsorbed or applied at a position where a structural defect, and particularly threading dislocation appears on a surface of the layer of a material on which is to be formed the semiconductor layer, so that structural defects, particularly threading dislocations in the semiconductor layer are suppressed, whereby a dislocation density can be significantly reduced.
Furthermore, in the present invention, a method for the formation of a semiconductor layer for forming the semiconductor layer comprises a first step for forming a buffer layer on a substrate; a second step for supplying a predetermined amount of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed on a surface of the buffer layer formed in the first step; a third step for forming the semiconductor layer on a surface of the buffer layer in which said structural defect suppressing material has been supplied onto the semiconductor layer to be formed in the second step; and a film thickness of the semiconductor layer in the third step being made to be 1 nm or thicker.
Therefore, according to the invention, a buffer layer is formed on a substrate in the first step, a predetermined amount of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed is supplied on a surface of the buffer layer in the second step, and the semiconductor layer is formed on a surface of the buffer layer onto which has been supplied the structural defect suppressing material in the third step in a film thickness of 1 nm or thicker, so that structural defects, particularly a density of threading dislocations can be significantly reduced in semiconductor layer formed by the structural defect suppressing material which has been supplied on the buffer layer with a predetermined amount so as to have a film thickness of 1 nm or thicker, while a number of structural defects, particularly threading dislocations appear in a buffer layer formed on a substrate.
The method for the formation of a semiconductor layer described in the immediately above paragraph may be arranged to further comprises a fourth step for supplying a predetermined amount of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed onto a surface of the semiconductor layer formed in the third step; a fifth step for forming the semiconductor layer on a surface of the semiconductor layer in which the structural defect suppressing material has been supplied onto the semiconductor layer to be formed in the fourth step; and implementing one or more times of the fourth step and the fifth step after finishing the third step.
As a result of the above modification, a predetermined amount of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed in the fourth step is supplied onto a surface of the semiconductor layer formed in the third step, a semiconductor layer is formed on a surface of the semiconductor layer onto which has been supplied the structural defect suppressing material in the fifth step, and one or more times of the fourth step and the fifth step are implemented after finishing the third step, so that a plurality of semiconductor layers can be laminated.
Moreover, the method for the formation of a semiconductor layer described in the above paragraph may be arranged in such that at least any of laser beam, electron beam, radical beam, ion beam, or atomic hydrogen is applied in at least either of the second step and the fourth step.
As a result of the above modification, surface diffusion in a surface onto which has been supplied a structural defect suppressing material is promoted, whereby the structural defect suppressing material is easily adsorbed or applied at positions on the surface where structural defects, and particularly threading dislocations appear, so that reforming of the surface can be more promoted in atomic level.
Furthermore, the method for the formation of a semiconductor layer described in the above paragraph may be arranged in such that a predetermined amount of plural types of structural defect suppressing materials for suppressing structural defects in the semiconductor layer to be formed are supplied in at least either of the second step and the fourth step.
As a result of the above modification, since a predetermined amount of plural types of structural defect suppressing materials are supplied in either of the above described second step and the fourth step, surface diffusion in a surface onto which have been supplied structural defect suppressing materials is promoted, whereby the structural defect suppressing materials are easily adsorbed or applied at positions where structural defects, and particularly threading dislocations appear on the surface, so that reforming of the surface can be more promoted in atomic level.
Moreover, a method for the formation of a semiconductor layer for forming the semiconductor layer comprises a first step for forming a buffer layer on a substrate; a second step for starting a supply of a material for forming the semiconductor layer to be formed as well as a supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed onto a surface of the buffer layer formed in the first step at the same timing, besides finishing the supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed at a timing prior to that of the supply of a material for forming the semiconductor layer to be formed; and a film thickness of the semiconductor layer in the second step being made to be 1 nm or thicker.
Therefore, according to the present invention, a buffer layer is formed on a substrate in the first step; a supply of a material for forming the semiconductor layer to be formed as well as a supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed onto a surface of the buffer layer are started at the same timing, besides the supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed is finished at a timing prior to that of the supply of a material for forming the semiconductor layer to be formed in the second step; and the semiconductor layer is formed in a film thickness of 1 nm or thicker, so that structural defects, particularly a density of threading dislocations can be significantly reduced in semiconductor layer formed by the structural defect suppressing material which has been supplied on the buffer layer with a predetermined amount so as to have a film thickness of 1 nm or thicker, while a number of structural defects, particularly threading dislocations appear in a buffer layer formed on a substrate.
A method for the formation of a semiconductor layer described in the immediately above paragraph may be arranged to further comprises a third step for starting a supply of a material for forming a semiconductor layer to be formed as well as a supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed onto a surface of the above described semiconductor layer formed in the second step at the same timing, besides finishing the supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed at a timing prior to that of the supply of a material for forming the semiconductor layer to be formed; and implementing at least one time of the third step after finishing the second step.
As a result of the above modification, a supply of a material for forming a semiconductor layer to be formed as well as a supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed onto a surface of the above described semiconductor layer formed in the second step are started at the same timing, besides the supply of a structural defect suppressing material for suppressing structural defects in the semiconductor layer to be formed is finished at a timing prior to that of the supply of a material for forming the semiconductor layer to be formed in the third step; and at least one time of the third step is implemented after finishing the second step, whereby a plurality of semiconductor layers can be laminated.
Furthermore, a method for the formation of a semiconductor layer described in the above paragraph may be arranged in such that at least any of laser beam, electron beam, radical beam, ion beam, or atomic hydrogen is applied in at least either of the second step and the third step.
As a result of the above modification, surface diffusion in a surface onto which has been supplied a structural defect suppressing material is promoted, whereby the structural defect suppressing material is easily adsorbed or applied at a position on the surface where structural defects, and particularly threading dislocations appear, so that reforming of the surface can be more promoted in atomic level.
Still further, a method for the formation of a semiconductor layer described in the above paragraph may be arranged in such that a predetermined amount of plural types of structural defect suppressing materials for suppressing structural defects in the semiconductor layer to be formed are supplied in at least either of the second step and the third step.
As a result of the above described modification, since a predetermined amount of plural types of structural defect suppressing materials for suppressing structural defects in the semiconductor layer to be formed are supplied in at least either of the second step and the third step, surface diffusion in a surface onto which has been supplied a structural defect suppressing material is promoted, whereby the structural defect suppressing material is easily adsorbed or applied at a position on the surface where structural defects, and particularly threading dislocations appear, so that reforming of the surface can be more promoted in atomic level.
Moreover, in a method f or the formation of a semiconductor layer in the above paragraphs, the above described substrate may be a silicon carbide substrate (6Hxe2x80x94SiC substrate, 4Hxe2x80x94SiC substrate), a laminated substrate of silicon carbide and silicon (SiC/Si substrate), a silicon substrate (Si substrate), a sapphire substrate (Al2O3 substrate), a laminated substrate of zinc oxide and sapphire (ZnO/Al2O3 substrate), a germanium substrate (Ge substrate), a gallium arsenide substrate (GaAs substrate), an indium arsenide substrate (InAs substrate), a gallium phosphide substrate (GaP substrate), an indium phosphide substrate (InP substrate), or a spinel substrate (MgAl2O3, LiGaO2); the above described structural defect suppressing material may be H (hydrogen) of the group I-A; Be (beryllium), or Mg (magnesium) of the group II-A; Al (aluminum), Ga (gallium), or In (indium) of the group III-B; C (carbon), Si (silicon), Ge (germanium), or Sn (tin) of the group IV-B; N (nitrogen), P (phosphorus), As (arsenic), or Sb (antimony); or O (oxygen), S (sulfur), Se (selenium), or Te (tellurium) of the group V-B in periodic table; and the semiconductor layer may be a layer of a semiconductor C (diamond), Si (silicon), Ge (germanium), SiC, SiGe, or SiCGe of the group IV; that of a binary system semiconductor of BN, AlN, GaN, InN, BP, AlP, GaP, InP, BAs, AlAs, GaAs, or InAs of the groups III-V; that of a ternary system mixed crystal semiconductor BAlN, BGaN, BInN, AlGaN, AlInN, GaInN, BAlP, BGaP, BInP, AlGaP, AlInP, GaInP, BAlAs, BGaAs, BInAs, AlGaAs, AlInAs, GaInAs, BNP, BNAs, BPAS, AlNP, AlNAs, AlPAs, GaNP, GaNAs, GaPAs, InNP, InNAs, or InPAs of the groups III-V; that of a quaternary system mixed crystal semiconductor BAlGaN, BAlInN, BGaInN, AlGaInN, BAlGaP, BAlInP, BGaInP, AlGaInP, BAlGaAs, BAlInAs, BGaInAs, AlGaInAs, BAlNP, BGaNP, BInNP, AlGaNP, AlInNP, GaInNP, BAlNAs, BGaNAs, BInNAs, AlGaNAs, AlInNAs, GaInNAs, BAlPAs, BGaPAs, BInPAs, AlGaPAs, AlInPAs, GaInPAs, BNPAs, AlNPAs, GaNPAs, or InNPAs of the groups III-V; or that of a semiconductor of ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, ZnCdO, ZnCdS, ZnCdSe, ZnCdTe, ZnOS, ZnOSe, ZnOTe, ZnSSe, ZnSTe, ZnSeTe, CdOS, CdOSe, CdOTe, CdSSe, CdSTe, CdSeTe, ZnCdOS, ZnCdOSe, ZnCdOTe, ZnCdSSe, ZnCdSTe, ZnCdSeTe, ZnOSSe, ZnOSTe, ZnOSeTe, ZnSSeTe, CdOSSe, CdOSTe, CdOSeTe, or CdSSeTe of the groups IIxe2x80x94VI in periodic table.
Furthermore, according to the present invention, a method for the formation of semiconductor layers on a substrate through a buffer layer comprises applying an MOCVD (Metalorganic Chemical Vapor Deposition), an MBE (Molecular Beam Epitaxy), a CBE (Chemical Beam Epitaxy), an HAVPE (Halide Vapor Phase Epitaxy), a GSMBE (Gas-Source Molecular Beam Epitaxy), an MOMBE (Metalorganic MBE), an LPE (Liquid Phase Epitaxy), a CVD (Chemical Vapor Deposition), a sputtering, or a vacuum deposition process; a first step for supplying solid gallium (Ga), trimethylgallium (TMG), or triethylgallium (TEG), solid aluminum (Al), trimethylaluminum (TMA), triethylaluminum (TEA), trimethylaminealum (TMAAl), dimethylethylaminealum (DMEAAl), or triisobutylaluminum (TIBAl) and nitrogen radical, ammonia (NH3), monomethylhydrazine (MMHy), ordimethylhydrazine (DMHY) on a surface of a SiC substrate or an Al2O3 substrate to form a GaN layer, an AlN layer, or an AlGaN layer as a buffer layer; a second step for supplying Si being a structural defect suppressing material used for a GaN layer, an AlN layer, or an AlGaN layer as a semiconductor layer to be formed in a film on a surface of the GaN layer, the AlN layer, or AlGaN layer as the buffer layer which has been formed in the first step with the use of solid silicon (Si), silane (SiH4), disilane (Si2H6), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2), diethylsilane ((C2H5)2SiH2), trimethylsilane ((CH3)3SiH), triethylsilane ((C2H5)3SiH), tetramethylsilane (TMSi), or tetraethylsilane (TESi); and a third step for supplying solid gallium (Ga), trimethylgallium (TMG), or triethylgallium (TEG), solid aluminum (Al), trimethylaluminum (TMA), triethylaluminum (TEA), trimethylaminealum (TMAAl), dimethylethylaminealum (DMEAAl), or triisobutylaluminum (TIBAl) and nitrogen radical, ammonia (NH3), monomethylhydrazine (MMHy), or dimethylhydrazine (DMHy) on a surface of a GaN layer, an AlN layer, or an AlGaN layer as the buffer layer to which has been supplied the Si in the second step to form a GaN layer, an AlN layer, or an AlGaN layer as the semiconductor layer in a thickness of 1 nm or thicker.
Therefore, according to the present invention, in a method for the formation of semiconductor layers on a substrate through a buffer layer, an MOCVD (Metalorganic Chemical Vapor Deposition), an MBE (Molecular Beam Epitaxy), a CBE (Chemical Beam Epitaxy), an HAVPE (Halide Vapor Phase Epitaxy), a GSMBE (Gas-Source Molecular Beam Epitaxy), an MOMBE (Metalorganic MBE), an LPE (Liquid Phase Epitaxy), a CVD (Chemical Vapor Deposition), a sputtering, or a vacuum deposition process is applied; solid gallium (Ga), trimethylgallium (TMG), or triethylgallium (TEG), solid aluminum (Al), trimethylaluminum (TMA), triethylaluminum (TEA), trimethylaminealum (TMAAl), dimethylethylaminealum (DMEAAl), or triisobutylaluminum (TIBAl) and nitrogen radical, ammonia (NH3), monomethylhydrazine (MMHy), or dimethylhydrazine (DMHY) are supplied on a surface of a SiC substrate or an Al2O3 substrate to form a GaN layer, an AlN layer, or an AlGaN layer as a buffer layer in the first step; Si being a structural defect suppressing material used for a GaN layer, an AlN layer, or an AlGaN layer as a semiconductor layer to be formed in a film is supplied on a surface of the GaN layer, the AlN layer, or AlGaN layer as the buffer layer with the use of solid silicon (Si), silane (SiH4), disilane (Si2H6), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2), diethylsilane ((C2H5)2SiH2), trimethylsilane ((CH3)3SiH), triethylsilane ((C2H5)3SiH), tetramethylsilane (TMSi), or tetraethylsilane (TESi) in the second step; and a third step for supplying solid gallium (Ga), trimethylgallium (TMG), or triethylgallium (TEG), solid aluminum (Al), trimethylaluminum (TMA), triethylaluminum (TEA), trimethylaminealum (TMAAl), dimethylethylaminealum (DMEAAl), or triisobutylaluminum (TIBAl) and nitrogen radical, ammonia (NH3), monomethylhydrazine (MMHy), or dimethylhydrazine (DMHy) are supplied on a surface of a GaN layer, an AlN layer, or an AlGaN layer as the above described buffer layer to which has been supplied the Si to form a GaN layer, an AlN layer, or an AlGaN layer as the semiconductor layer in a thickness of 1 nm or thicker in the third step. As a result, Si is adsorbed on the surface of a GaN layer, an AlN layer, or an AlGaN layer, whereby the surface of the GaN layer, the AlN layer, or the AlGaN layer is reformed in atomic level, and thereafter another GaN layer, AlN layer, or AlGaN layer is formed as a semiconductor layer, so that a defect density of structural defects, particularly a dislocation density of threading dislocations in the GaN layer, the AlN layer, or the AlGaN layer being the semiconductor layer can be significantly reduced.
In addition, since Si supplied as a structural defect suppressing material is a metal used as an n-type impurity material for a GaN layer, an AlN layer, or an AlGaN layer, it does not affect adversely quality of the resulting semiconductor layer in case of forming the GaN layer, the AlN layer, or the AlGaN layer as an n-type semiconductor layer, and thus, such Si can be easily supplied.
Moreover, according to the present invention, a method for the formation of a semiconductor layer in which a GaN layer or an AlGaN layer is formed on an Sic substrate or an Al2O3 substrate by means of MOCVD (Metalorganic Chemical Vapor Deposition) equipment comprises a first step for either supplying trimethylgallium (TMG) or triethylgallium (TEG) and ammonia (NH3) onto a surface of the SiC substrate or the Al2O3 substrate to form a GaN layer as a buffer layer, or supplying trimethylgallium (TMG) or triethylgallium (TEG) and trimethylaluminum (TMA) or triethylaluminum (TEA) and ammonia (NH3) thereon to form an AlGaN layer as a buffer layer; a second step for supplying Si being an n-type impurity material used for a GaN layer or an AlGaN layer on a surface of the GaN layer or the AlGaN layer being the buffer layer formed in the first step with the use of silane (SiH4), disilane (Si2H6), or tetraethylsilane (TESi) in one monolayer or less; and a third step for either supplying trimethylgallium (TMG) or triethylgallium (TEG) and ammonia (NH3) on a surface of the GaN layer or the AlGaN layer being the buffer layer to which has been supplied the silane (SiH4), disilane (Si2H6), or tetraethylsilane (TESi) in the second step to form a GaN layer in a thickness of 1 nm or thicker, or supplying trimethylgallium (TMG) or triethylgallium (TEG) and trimethylaluminum (TMA) or triethylaluminum (TEA) and ammonia (NH3) to form a AlGaN layer in a thickness of 1 nm or thicker.
Therefore, according to the present invention, in a method for the formation of a semiconductor layer in which a GaN layer or an AlGaN layer is formed on an SiC substrate or an Al2O3 substrate by means of MOCVD (Metalorganic Chemical Vapor Deposition) equipment, either trimethylgallium (TMG) or triethylgallium (TEG) and ammonia (NH3) are supplied onto a surface of the SiC substrate or the Al2O3 substrate to form a GaN layer as a buffer layer, or trimethylgallium (TMG) or triethylgallium (TEG) and trimethylaluminum (TMA) or triethylaluminum (TEA) and ammonia (NH3) are supplied thereon to form an AlGaN layer as a buffer layer in the first step; Si being an n-type impurity material used for a GaN layer or an AlGaN layer is supplied on a surface of the GaN layer or the AlGaN layer being the buffer layer with the use of silane (SiH4), disilane (Si2H6), or tetraethylsilane (TESi) in one monolayer or less in the second step; and either trimethylgallium (TMG) or triethylgallium (TEG) and ammonia (NH3) are supplied on a surface of the GaN layer or the AlGaN layer being the buffer layer to which has been supplied the silane (SiH4), disilane (Si2H6), or tetraethylsilane (TESi) to form a GaN layer in a thickness of 1 nm or thicker, or trimethylgallium (TMG) or triethylgallium (TEG) and trimethylaluminum (TMA) or triethylaluminum (TEA) and ammonia (NH3) are supplied thereon to form a AlGaN layer in a thickness of 1 nm or thicker in the third step.
Hence, Si in the silane (SiH4), disilane (Si2H6), or tetraethylsilane (TESi) is adsorbed on a surface of a GaN layer, or an AlGaN layer, whereby the surface of the GaN layer, or the AlGaN layer is reformed in atomic level, and thereafter another GaN layer, or AlGaN layer is formed as a semiconductor layer, so that a defect density of structural defects, particularly a dislocation density of threading dislocations in the GaN layer being a semiconductor layer can be significantly reduced.
In addition, since Si supplied as a structural defect suppressing material is a metal used as an n-type impurity material for a GaN layer, or an AlGaN layer, it does not affect adversely quality of the resulting semiconductor layer in case of forming the GaN layer, or the AlGaN layer as a semiconductor layer, and thus, such Si can be easily supplied.